Connected: An Internet Encyclopedia
RFC 1521 - Appendix E -- IANA Registration Procedures

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### Appendix E -- IANA Registration Procedures

MIME has been carefully designed to have extensible mechanisms, and it is expected that the set of content-type/subtype pairs and their associated parameters will grow significantly with time. Several other MIME fields, notably character set names, access-type parameters for the message/external-body type, and possibly even Content-Transfer-Encoding values, are likely to have new values defined over time. In order to ensure that the set of such values is developed in an orderly, well-specified, and public manner, MIME defines a registration process which uses the Internet Assigned Numbers Authority (IANA) as a central registry for such values.

In general, parameters in the content-type header field are used to convey supplemental information for various content types, and their use is defined when the content-type and subtype are defined. New parameters should not be defined as a way to introduce new functionality.

In order to simplify and standardize the registration process, this appendix gives templates for the registration of new values with IANA. Each of these is given in the form of an email message template, to be filled in by the registering party.

#### E.1 Registration of New Content-type/subtype Values

Note that MIME is generally expected to be extended by subtypes. If a new fundamental top-level type is needed, its specification must be published as an RFC or submitted in a form suitable to become an RFC, and be subject to the Internet standards process.

          To:  IANA@isi.edu
          Subject:  Registration of new MIME
               content-type/subtype

          MIME type name:

          (If the above is not an existing top-level MIME type,
          please explain why an existing type cannot be used.)

          MIME subtype name:

          Required parameters:

          Optional parameters:

          Encoding considerations:

          Security considerations:

          Published specification:

          (The published specification must be an Internet RFC or
          RFC-to-be if a new top-level type is being defined, and
          must be a publicly available specification in any
          case.)

          Person & email address to contact for further information:

#### E.2 Registration of New Access-type Values for Message/external-body

          To:  IANA@isi.edu
          Subject:  Registration of new MIME Access-type for
               Message/external-body content-type

          MIME access-type name:

          Required parameters:

          Optional parameters:

          Published specification:

          (The published specification must be an Internet RFC or
          RFC-to-be.)

          Person & email address to contact for further information:

Next: Appendix F -- Summary of the Seven Content-types

Connected: An Internet Encyclopedia
RFC 1521 - Appendix E -- IANA Registration Procedures